The dorsal blood vessel is part of the circulatory system of the earthworm that carries blood to the front of its body. It is a single structure that runs along the back of the worm's body.
The dorsal blood vessel is part of a circulatory system that is classified as closed. The system carries blood through the earthworm's body. The dorsal vessel is one of three main vessels, the other two being the aortic arch and the ventral blood vessel. The aortic arch pumps blood to the dorsal and ventral vessels. The ventral vessel carries blood to the back of the earthworm's body.